Conventional volatile memory cells, such as dynamic random access memory (DRAM) cells, may include a storage element and a transistor. The storage element may, for example, include a capacitor (e.g., sometimes referred to as a “cell capacitor” or a “storage capacitor”) configured to store a logical state (e.g., a binary value of either a “0” or a “1”) defined by the storage charge in the capacitor. The transistor may be referred to in the art as an “access transistor.” The transistor conventionally includes a channel region between a pair of source/drain regions and further includes a gate configured to electrically connect the source/drain regions to one another through the channel region. The channel region conventionally includes a semiconductor material, such as silicon.
To charge, discharge, read, or recharge the capacitor, the transistor may be selectively turned to an “on” state, in which current flows between the source and drain regions through the channel region of the transistor. The transistor may be selectively turned to an “off” state, in which the flow of current is substantially stopped. In the off state, it is desired for the capacitor to retain the charge, without change. However, capacitors of conventional volatile memory cells may exhibit discharges of current over time and a resulting loss in stored charge. Therefore, even in the “off” state when the memory cell is unselected, current may flow from the capacitor. This off-state leakage current is referred to in the art as a sub-threshold leakage current.
Due to sub-threshold leakage current, conventional volatile memory cells are frequently refreshed. The sub-threshold leakage current may also impact the fabrication and configuration of an array of memory cells within a memory device. Sub-threshold leakage current rates, refresh rates, cell size, and thermal budgets of memory cells are often important considerations in the design, fabrication, and use of volatile memory cells and arrays of cells incorporated in memory devices.
Methods of forming channel regions often include etching the channel regions of such structures with a wet etchant such as oxalic acid. However, the use of such etchants often forms a residue on such structures. The residue left behind by such etchants may change the material properties of the channel regions. In addition, wet etchants are often unable to achieve a desirably high packing density of the structures being patterned.